Syracuse

Occurrence of 40 sanitary indicators in French digestates derived from different anaerobic digestion processes and raw organic wastes from agricultural and urban origin

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Wybraniec, Caroline | Gagne, Geneviève | Moussard, Cécile | Beaupère, Marion | Lusurier, Léa | Leriche, Françoise | Marjolet, Laurence | Sertillanges, Nicolas | Patureau, Dominique | Cournoyer, Benoit | Galia, Wessam

Edité par CCSD -

International audience. To date, there is no scientific consensus on the fate of pathogenic bacteria present in raw organicwastes and the sanitary quality of digestates. This work aims to characterize the influence of thenature of raw wastes as well as the types of processes on the sanitary quality of digestates. For thispurpose, the occurrence and the fate of 41 sanitary indicators including pathogenic bacterial species,antimicrobial resistance genes as well as new indicators of health hazard such as virulence factorscarried by mobile genetic elements were monitored during anaerobic digestion (AD). Three full-scaleplants were selected to study the effect of the key parameters of the AD process (type of alimentation,number of steps, temperature, pH). While the impact of the nature of raw wastes has been studiedwith 3 lab-scale reactors where the AD process was similar (semicontinuous, mesophilic) but theproportions of inputs have been varied (mainly fecal matters supplemented or not with straw or strawand zeolite). First, the prevalence of these indicators was measured in digestates and compared withthat measured in raw wastes. Of the 13 species studied, only one (Streptococcus agalactiae) wascompletely removed, regardless of the process and nature of the waste used. For virulence factorsand mobile genetic elements, no significant decrease in prevalence could be detected. In a secondstep, absolute quantification of the indicators displayed a high prevalence in raw wastes has beendone using a Digital Droplet PCR system. Regarding the effect of the nature of raw waste, the reactorsfed with fecal matter supplemented with straw (Lab2) or with straw and zeolite (Lab3) have a higherhygienization efficiency compared to reactor fed uniquely with fecal matter (Lab1). Thus, 2pathogenic species (Enterococcus faecalis, Enterococcus faecium) and 3 mobile genetic elements(intI1, intI2 and IS26) were significantly decreased in both reactors (Lab2 and Lab3). Nevertheless,1 mobile genetic element (intI1) and 1 antibiotic resistance gene (tetO) have been significantlyincreased in Lab1. Interestingly, of 13 polycyclic aromatic hydrocarbons (PAHs) and 13pharmaceutical products measured in this study, the quantities of 11 PAHs and 11 pharmaceuticalproducts, were significantly higher in Lab1 samples (treated or not) than in Lab2 and Lab3 samples.The high concentration of some micropollutants such as triclosan found in Lab1 samples couldexplain the lower hygienization efficiency of AD process in this reactor compared to the otherreactors (Lab2 and Lab3). Regarding the impact of the type of process, the fed-batch reactor had abetter hygienization effect with a total reduction of a virulence factor (ybtA), involved in theproduction of siderophores, and a significant reduction of enterotoxigenic Escherichia coli. Thisstudy showed that the sanitary quality of digestate is first related to the sanitary quality of raw wasteand then to the employed process.

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